An aerofoil blisk comprises a plurality of blades welded onto a disc so as to extend radially outwardly therefrom. Blisks may be used in aero engines both in the compressor and turbine and can be advantageous over conventionally bladed discs.
It is known to join the blades to the disc by linear friction welding, this being a process whereby one part is held stationary while the other part is oscillated against it under load, the heat generated and the applied loads resulting in a weld as material extrudes from the edges of the joint. In the making of blisks, a blade member (which will subsequently be machined to form the finished blade) is oscillated relative to a stationary disc whilst a load is applied in the radial direction of the blade, towards the disc. The blade is thereby joined to the disc. The radially inner end of the blade which joins to the disc is referred to as a stub.
Excess material is subsequently machined away from the blade member, to result in a blade of the desired shape.